A display device such as a liquid crystal display device (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), a cathode-ray tube (CRT), a fluorescent indicator tube or a field emission display displays a color image with a combination of the three primary colors (i.e., red, blue, green). However, it is very difficult (substantially impossible) to use the ideal three primary colors. For example, the plasma display panel uses phosphors of the three primary colors, which emit light containing an unnecessary component (in the wavelength region of 560 to 620 nm). Therefore, it has been proposed to correct the color balance of the displayed image by an optical filter absorbing the unnecessary component. The optical filter for the color correction is described in Japanese Patent Provisional Publication Nos. 58(1983)-153904, 60(1985)-118748, 60(1985)-18749, 61(1986)-188501, 3(1991)-231988, 5(1993)-203804, 5(1993)-205643, 7(1995)-307133, 9(1997)-145918, 9(1997)-306366 and 10(1998)-26704.
The display device needs prevention of reflection as well as the color collection. On the screen of the display device, the surrounding scene is often reflected to impair the contrast of the displayed image. Various anti-reflection films have been proposed to solve the problem of reflection. The known anti-reflection layers are categorized into two types, namely evaporating (and depositing) layers and coating layers. The evaporating layers are superior to the coating layers in view of optical characteristics, but the coating layers are easily formed compared with the evaporating layers.
The evaporating layers have been used as anti-reflection films for lenses of glasses or cameras. The layers are generally formed by a vacuum deposition process, a spattering method, an ion plating method, a CVD method or a PVD method.
The coating layers can be formed by coating a dispersion of fine particles and a binder. The coating layers are described in Japanese Patent Provisional Publication Nos. 59(1984)-49501, 59(1984)-50401, 60(1985)-59250 and 7(1995)-48527.
The anti-reflection layers can be introduced into the optical filters. The optical filters having the anti-reflection layers are disclosed in Japanese Patent Provisional Publication Nos. 61(1986)-188501, 5(1993)-205643, 9(1996)-145918, 9(1996)-306366 and 10(1997)-26704. The optical filter described in 61(1986)-188501, 5(1993)-205643, 9(1996)-145918 or 9(1996)-306366 has a transparent support containing a dye or a pigment so that the support functions as an optical filter. Further, the optical filter described in 10(1997)-26704 comprises a colored hard coating (surface hardening) layer provided between a support and an anti-reflection layer, so that the hard coating layer functions as an optical filter.